In Service Studio you can expose entities owned by your eSpace to be used by a different one. In this context, eSpaces are called Producer and Consumer, respectively.
How to Expose an Entity
In a Producer eSpace, simply set the Public property of an entity to Yes and publish the eSpace. How
You can expose any entity of your eSpace even if it has attributes that are identifiers of other entities that are not public. This is very useful because you can expose only the entities relevant to Consumer eSpaces, without having to expose your entire data model.
How to Expose an Entity as Read Only
To protect data records of an exposed entity from being written in another eSpace, set the Expose Read Only property to Yes. How
Use Entity References | Entity Properties